Spark plug



H. RABEZZANA SPARK PLUG Filed March 2'7. 193'? Sept. 13, 1938.

Patented Sept. 13, 1938 SPARK PLUG Hector Rabezzana, Flint, Mich, assignor to Gen-- eral Motors Corporation, Detroit, Mich., a corporation of Delaware Application March 27, 1937, Serial No. 133,341

6 Claims.

My invention relates to spark plugs for internal combustion engines, and particularly to means located adjacent the upper end of the hollow shell or casing of the plug for holding the insulating member thereof in place within the casing. Said holding means is in the nature of a gasket at the upper end of the shell, although perfect gas tightness of the plug is secured for the most part by a yieldable gasket within and adjacent the lower end of the shell.

The holding means comprises a resilient annular metallic member surrounding and resting upon a shoulder provided adjacent the upper end of the insulating member of the plug when it is assembled within the shell and means, which may take various specific forms, for holding said member and the insulating member in place within the hollow shell. Said annular member is curved or C-shaped in cross-section and, being made of a metal such for example as spring steel selected with that end in view, it is resilient and, due to its form as hereinafter appears, acts like an extremely stiif spring against an upper shoulder of the insulating member and forces said member against a suitable gasket which is supported by an internal ledge located adjacent the lower end of the shell.

The drawing submitted herewith illustrates various embodiments of my invention adapted in each case to hold an insulating member in place within the shell or casing of a spark plug; and the particular features wherein my invention consists are enumerated in the claims at the end of this specification.

In the drawing:

Figure 1 is a fragmentary view partly in section showing my invention used to hold the insulating member of a glow plug in place in a passage provided for it.

Figure 2 is a similar view showing my invention used with a spark plug, to hold the insulating member thereof in place within the shell or casing of the plug.

Figure 3 is a view showing the annular metallic resilient holding member of my invention by itself, and upon a larger scale than in Figures 1 and 2.

Figure 4 is a fragmentary view showing an alternative method of securing the annular holding member and the insulating member in place.

Figures 5 and 6 are fragmentary views showing still another method of securing the annular holding member in place within the upper end of the shell of the plug.

Referring to the drawing, the numeral l0 designates the hollow metallic shell or casing of a spark plug, the same having an internal ledge l I adjacent its lower end which supports the insulating member l2; a suitable gasket l3 or equivalent means for securing a gas tight joint between the insulating member and the shell being shown between said ledge and a lower shoulder H of the insulator. When as shown in Figure 1 my inventionis used in connection with a glow plug having a longer insulating member l5 than is ordinarily used in spark plugs, said member is commonly housed within a passage in a cylinder head l6 and is supported by an internal ledge like the ledge H against which the insulator is forced by a gland nut I! in threaded engagement with the upper end of said passage.

The insulating member has an annular shoulder l8 adjacent its upper end; and the numeral l9 designates an annular resilient member 0- shaped in cross-section which surrounds the upper part of the insulating member and rests upon said shoulder, and which annular member (in Figure 2) is held in place within the shell by an inturned holding flange 20 at the upper extremity of the shell. This annular G-shaped member is made up of a lower part |9l which engages the shoulder l8, an upper part l92 which is engaged by and lies beneath the holding flange 20 (as in conventional single piece spark plugs), and an intermediate part I93 which is offset toward the axis of the insulating member I2 and is stressed as force is applied to the upper part as the flange 20 is turned inward and forced against said upper part in assembling the plug. It therefore fol lows that in the finished plug the insulating member is forced against the ledge II by the C- shaped member which acts as an extremely stiff spring, which yields during the assembling of the parts, and which in the finished plug acts to force the insulating member toward the ledge II and maintain gas tightness thereof when the plug is in use; such gas tightness, as stated, being due for the most part to the intimate joint thus secured between the ledge II and the lower shoulder M of the insulating member.

In Figure 1 a washer 2| is interposed between the upper extremity of an annular resilient member 22 which acts against an upper shoulder 23 upon the insulating member l5, said washer being held in place by an inturned flange 24 of the gland nut II. The member 22, however, is similar in action to the member l9 and acts in the same way to force the insulating member l5 against a lower ledge at 25, although in this embodiment of my invention the resilient member 22 is subjected to pressure by screwing the gland nut ll into the upper end. of the passage provided for the insulating member l5, rather than during a turning inward operation whereby the flange 24 is formed. In both forms, however, the insulating member of the plug is held in place and forced against a lower or inner supporting ledge by a resilient member of C-shape cross-section, which acts as a stiff spring to hold the insulator in place and maintain a gas tight joint at the lower or inner end of the plug.

The insulating member and the resilient shaped member may be held in place within the shell 0! the plug by a gland nut, as in conventional plugs not of the single piece type. Thus Figure 4 shows the insulator 23 as having an upper shoulder 21 against which an annular resilient member 23 acts precisely as in the forms oi my invention illustrated in Figures 1 and 2, but in this form pressure to compress said member and bring about its resilient holding i'unction is produced by screwing a gland nut 23 into the upper end 01 the passage within the shell 30 provided for the insulating member.

The periphery of the lower end I3i oi the resilient C-shaped member (see Figure 2) is spaced slightly away from the interior oi the passage in the shell provided for it and the insulating member, as at 3|, so that said lower end may adapt itself to the upper shoulder of the insulating member during the assembling of the parts without binding, as might be the case ii the periphery of said lower end came into contact with the interior 01' said passage during the assembling of the parts. Such spacing, moreover, results in a more free and unrestrained action oi said member as a spring as its lower end is, to a degree, free to move sidewise as it is subjected to axial compression during the assembling of the parts within the hollow shell or casing 01' the plug.

As an alternative method 01' securing the C- shaped annular resilient member in place within the hollow shell 01 the plug I may, as shown in Figures 5 and 6, form an internal groove 32 in the inner cylindrical wall of the shell 33, which must obviously be initially large enough in diameter to receive the insulating member 34 and the resilient member 35 which as hereinbefore engages with an annular shoulder 33 adjacent the upper end of the insulating member; the upper end of the member 35 occupying a position slightly above the groove, as shown, when the parts are placed loosely within the shell and before said member is compessed and permanently fastened in place within the upper end of the shell.

The resilient member is next forced downward as by a suitable press having a hollow plunger or ram, thus forcing the lower shoulder of the insulating member against a ledge within the casing and the lower end of the resilient member 33 into firm engagement with the upper shoulder 36, and setting up a force in said member which tends to elongate it, and which force acts resiliently throughout the life of the plug to always force the insulating member toward the inner annular supporting ledge adjacent the lower end of the shell.

Then and while the parts are held with the upper end of the c-shaped member 35 down and opposite the groove 32 the upper end of the shell 33 is constricted and forced inward, as by a plunger or ram having a conical recess in its lower end, during which step the periphery of the upper end of the C-shaped member 35 enters the groove 32 thus locking said member in place under compression as will be understood from Figure 6 01' the drawing.

Having thus described and explained my invention, I claim and desire to secure by Letters Patent:

1. In a spark plug and in combination with an insulating member having an annular shoulder adjacent its upper end; an annular metallic resilient member c-shaped in crosssection surrounding said insulating member and restingupon said shoulder, and which member comprises lower and upper parts spaced apart from one another and an intermediate part oflset toward the axis 01 said insulating member; and means engaging the upper end of said resilient member for holding it and said insulating member in place within a suitable shell or casing.

2. In aspark plug, a hollow shell; an insulating member supported within said shell, and which member has an annular shoulder adjacent its upper end; an annular metallic resilient member C-shaped in cross-section surrounding said insulating member and resting upon said shoulder, and located within the upper end 0! said shell, and which member comprises lower and upper parts spaced apart from one another and an intermediate part oifset toward the axis of said insulating member; and means engaging the upper end of said resilient member for holding it and said insulating member in place within said shell.

3. In a spark plug, a hollow shell; an insulating member supported within said shell, and which. member has an annular shoulder adjacent upper end; an annular metallic resilient member C-shaped in cross-section surrounding said insulating member and resting upon said shoulder, and located within the upper end of said shell, and which member comprises lower and upper parts spaced apart from one another and an intermediate part offset toward the axis oi said insulating member; and an inturned flange at the upper end of said shell and engaging the upper end of said resilient member for holding it and said insulating member in place within said shell.

4. In a spark plug, a hollow shell having an internal ledge adjacent its lower end; an insulating member within said shell and supported by said ledge, and which member has an annular shoulder adjacent its upper end; an annular metallic resilient member C-shaped in cross-section surrounding said insulating member and resting upon said shoulder, and located within the upper end 01' said shell, and which member comprises lower and upper parts spaced apart from one another and an intermediate part oilset toward the axis of said insulating member; and an in turned flange at the upper end of said shell and overlying the upper end of said resilient member for holding it and said insulating member in place within said shell.

5. In a spark plug, a hollow shell having an internal groove adjacent its upper end; an insulating member supported within said shell, and which member has an annular shoulder adjacent its upper end; and an annular metallic resilient member C-shaped in cross-section surrounding said insulating member and resting upon said shoulder, and the upper end of which resilient member lies within said groove.

6. In a spark plug, a hollow shell having an internal ledge adjacent its lower end, and an internal groove adjacent its upper end; an insulating member within said shell and supported by said ledge, and which member has an annular shoulder adjacent its upper end; and an annular metallic resilient member C-shaped in cross-section surrounding said insulating member and resting upon said shoulder, and the upper end of which resilient member lies within said groove.

HECTOR RABEZZANA.

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